Compositions useful for inducing a tan on the human epidermis without the assistance of exposure to the sun have been known for many years. For example, U.S. Pat. No. 2,949,403 discloses that the compound dihydroxyacetone(DHA) can be used for this purpose; Since that report, DHA has been widely employed in commercial self-tanners. Many variations on the basic DHA formulation have been proposed to overcome or bolster some of the inherent inadequacies observed when using DHA alone as the active agent in a formulation. For example, DHA tends to impart an unpleasant orange cast to the skin of fair-skinned individuals; to compensate for this deficiency, various dyes have been incorporated with DHA(U.S. Pat. No. 4,708,865). Moreover, DHA has also been incorporated into formulations with sunscreens, such as octyl methyl PABA(e.g., U.S. Pat. Nos. 4,434,154 and 3,177,120).
Additional difficulties arise with the formulation of DHA for efficient application to the skin. DHA is understood to work by reacting with skin proteins and amino acids to elicit the skin-coloring effect. Standard formulations of DHA are usually creams or lotions from which the DHA must diffuse from the base into the skin to effect the color change. The usual excipients used in these formulations, e.g., emulsifiers, oils, waxes, and the like, frequently trap a portion of the DHA in a surface film on top of the skin, thereby reducing its ability to penetrate the epidermis properly, where it must be located to accomplish the desired effect. The failure to penetrate results in a loss of depth and longevity of the artificial tan.
As the evidence accumulates as to the damaging effects of prolonged exposure to the sun, the importance of self-tanners has grown concurrently. As the demand for self-tanners has increased, however, so has consumer demand for a tanner which has a natural looking color, and which produces a longer lasting tan. Therefore, there continues to be a need for a self-tanning composition which meets these criteria. The present invention now satisfies these consumer needs.